Grinding machine for gems

ABSTRACT

A machine for grinding square and rectangular shaped cabochons of semiprecious gems in which the size and shape are mechanically controlled.

United States Patent 11 1 Marsha Nov. 27, 1973 [54] GRINDING MACHINE FOR GEMS 2,956,377 10/1960 White 51/100 R [76] Inventor: Edwin G Marsha", O- OX 1745 3,279,127 10/1966 Glezentanner 125/30 R X Nq lqs A [22] Filed: May 9, 1972 Prima ExaminerI-lar0ld D. Whitehead [211 pp No 251 659 Att0rneyWarren F. B. Lindsley [52] US. Cl 51/100 R 511 Int. Cl B24b 17/00 [57] ABSTRACT [58] Fleld of Search 51/229, IO(IJ:Z;IZ37 A machine for g g Square and rectangular shaped cabochons of semiprecious gems in which the size and Reerences Cited shape are mechanically controlled.

UNITED STATES PATENTS 5 Claims 8 Drawing Figures 3,568,369 3/1971 Marshall 51/100 R Patented Nov. 27, 1973 3,774,347

75 Sheets-Sheet 1 Win;

I l imJxi -42 Jan-5,4

Patented Nov. 27, 1973 3,774,347

3 Sheets-Sheet 2 Patented Nov. 27, 1973 3,774,347

3 Shee ts-Sheet 3 13: 50. EEC-. 52, 13:1 -5:

1 GRINDING MACHINE FOR GEMS BACKGROUND OF THE INVENTION This invention pertains to template controlled grinding machines, and more particularly to a grinding machine for grinding square and rectangular shaped cabochons of semiprecious gems that automatically reproduces the work in a rapid high production manner.

While large quantities of jewelry mountings for square and rectangular stones have been made heretofore, they have been filed by the faceting method using only the best of semi-precious gems. A great amount of time is required by professional gem cutters using these former methods in laboriously making a properly shaped and finished cabochon of acceptable quality.

SUMMARY OF THE INVENTION In accordance with the objects of this invention, an improved gem grinding machine is provided which makes cushion type cabochons from rough semiprecious gems in much less time than heretofore possible.

It is, therefore, one object of this invention to provide an improved automatic grinding machine to grind agate and other semi-precious materials to form sqaure and rectangular shaped cabochons.

Another object of this invention is to provide a gem grinding machine which enables the most amateur of rockhounds and collectors to make as accurate a square or rectangularly shaped cabochon as a professional with many years experience using hand methods.

A further object of this invention is to provide a gem grinding machine of reasonable cost which mechanizes the grinding of square or rectangular cabochons.

A still further object of this invention is to provide a machine that does away with present hand methods while automatically sizing and shaping the cabochon without skill and care upon the part of the operator.

Further objects and advantages of the invention will become apparent as the following description proceeds and the features of novelty which characterize this invention will be pointed out with particularity in the claims annexed to and forming part of this specification.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention may be more readily described by reference to the accompanying drawings, in which:

FIG. 1 is a front elevation of the grinding machine incorporating the features of this invention;

FIG. 2 is a sectional view of the grinding machine shown in FIG. 1 taken along the line 2-2;

FIG. 3 is a fragmentary sectional view taken on the line 3-3 of FIG. 1;

FIG. 4 is a fragmentary sectional view taken on the line 44 of FIG. 2;

FIG. 5 is a fragmentary view showing different positions of a stone as it is ground in the grinder; and

FIGS. 60, 6b and 6c show solenoid indexing positions.

DESCRIPTION OF THE PREFERRED EMBODIMENT As an example of one embodiment of the present invention, FIGS. 1-3 illustrate a gem grinding machine 9 which comprises a base 10 upon which are mounted suitable bearing supports 11 and 12 for a grinding wheel spindle 13. The spindle 13 has a conventionally mounted grinding wheel 14 thereon which is driven by a suitable motor (not shown) through a belt 14a and a pulley 14b, the latter being mounted on the spindle 13. The grinding wheel 14 is provided with a suitable shield 15 mounted on the base 10.

A template and work support arm 16 has integral upper and lower link pieces 17 on the other ends of which are pivotally mounted on aligned trunions 18 which define a vertical axis 19 about which the arm 16 is pivotable.

The trunions 18 are mounted on the outer ends of upper and lower brackets 20 of a feed frame 21 which is in turn pivotally mounted to swing about a vertical axis 22-of a support column 23 fixed to the base 10.

The upper link piece 17 of arm 16 is provided with a pair of adjusting screws 24 which are arranged to be adjustably threaded into engagement with opposite side edges 25 of the upper bracket 20 of the feed frame 21. This adjustment will set and lock the angular relationship between the arm 16 and the feed frame 21, and is needed to ensure that the arm 16 presents a workpiece 26 mounted thereon (as will be described) normal to the periphery 27 of the grinding wheel 14. Periodic adjustment of this angular relationship will be needed to compensate for normal wear of this grinding wheel 14.

I The feed frame 21 is arranged to pivot about the axis 22 of the column 23 to swing the arm 16 which is attached thereto into and out of the working position to allow access to the workpiece 26.

A tension spring 28 is removably secured on one of its ends to a pin 29 carried on the arm 16, and is attached on its other end to an ear 30 fixed on the shield 15 of the grinding wheel 14. With the spring 28 mounted in this fashion, the frame 21 and the arm 16 are yieldingly urged toward the periphery of the grinding wheel 14.

The workpiece 26 is carried in a lower reciprocating assembly 31 mounted on the support arm 16. An identical upper reciprocating assembly 32, which has a master template 33 mounted thereon, is also attached to the support arm 16.

The workpiece 26 is mounted on a shank 34 and the master template 33 has a similar shank 35, and these shanks are mountedwithin their reciprocating assemblies 31 and 32 so as to be parallel with respect to each other, and laterally extend therefrom equal distances.

The workpiece 26 in the form of a stone to be ground is replacably attached to the end of its shank 34 such as by suitable adhesive. The shank 34 is rotatably carried in a fixed axial position within a bore 36 formed in a spindle 37.

The master template 33 is preferably formed of metal and has its shank 35 mounted in the same manner within a bore 38 formed in a spindle 39.

The shanks 34 and 35 both extend from their respective spindles 37 and 39 and are axially fixed thereto by rotational indexing wheels 40 and 41 suitably attached thereto by nuts 42.

The indexing wheels 40 and 41 provide rotational movement to their respective shanks 34 and 35 as will hereinafter be described in detail.

The spindles 37 and 39 are reciprocally driven in a synchronous manner by a motor 43 mounted atopthe support arm 16. The motor 43 has a drive shaft 44 which has a crank arm 45 attached thereto for rotation in a circular path. An upper drive lever 46 is pivotally mounted to the crank arm 45 and has its lower end pivotally secured to the spindle 39. A lower drive lever 47 is pivotally mounted on its upper end to the spindle 39 and on its lower end to the spindle 37.

The synchronous reciprocal movement provided by the motor 43 and the drive levers 46 and 47 will drive both of the spindles 37 and 39 through an arcuate path as dictated by an upper guide assembly 48 on which the spindle 39 is mounted and by a lower guide assembly 49 upon which the spindle 37 is mounted.

The guide assemblies 48 and 49 are identical and the mounting of the spindles 37 and 39 thereon is accomplished in the same manner. Therefore, only the lower guide assembly 49 will now be described in detail.

As seen best in FIGS. 2 and 4, the guide assembly 49 includes a guide plate 50 which is fixedly attached in contiguous flush engagement with the arm 16 such as by screws 51. The plate 50 is provided with a T-shaped in transverse cross section slot 52 formed therein which defines the arcuate path that the spindle 37 will follow. The slot 52 has the shank portion 53 of its T-shape facing outwardly with respect to the arm 16 and has the transverse portion 54 of the T-shape formed in the surface of the plate 50 which is adjacent the arm 16. An arcuate slide bar 55 is captively held in the portion 54 of the slot 52 and is slidable therein. A stud 56 is integrally formed with the slide bar 55 and extends therefrom through the shank portion 53 of the T-shaped slot 52, and extends through an aperture 57 formed in the spindle 37. The outermost end of the stud 56 has the lower end of the lower drive lever 47 pivotally mounted thereon, and is provided with a threaded portion upon which a suitable nut 58 is mounted to secure the lever and spindle thereto.

The upper reciprocating assembly 32 is the same as the lower assembly 31 with the exception that its stud 56 is slightly longer so that both of the drive levers 46 and 47 may be pivotally secured thereto by its mounting nut 58.

Movement of the spindles 37 and 39 through their arcuate paths will result in a rocking motion being applied to the workpiece 26 and to the master template 33. This movement may be best seen in FIG. where it is illustrated as it applies to the spindle 37 and the workpiece 26.

At the start of the grinding operation the spindle 37 will be at the lowermost point of travel through its arcuate path. This position as seen in solid lines in FIG. 5 places the center 59 of the workpiece in contact with the grinding wheel 14. The upper limit of travel of the spindle 37 is shown in dotted lines in the same figure as having rocked the workpiece 26 to place the mounting edge 60 thereof in contact with the wheel 14.

It may now be seen that one cycle of the spindle 37 will grind a single radial path from the center 59 to the edge 60 of the workpiece, and the contour of this path will be dictated by the contour of the master template 33.

The template 33 is performed into the desired contour and is positioned to engage a wear plate 61 located on the outer end of a longitudinally adjustable shaft 62 carried in an appropriate supporting structure 63 fixed to the shield of the grinding wheel 14. The adjustment of the wear plate 61 is employed to compensate for normal wear of the wheel 14 and is accomplished by jam nuts 64 on the threaded end of the shaft 62 and a lug 65 fixed on the supporting structure 63.

It may now be seen that the spring 28 will yieldingly bias the frame 21 and thus the arm 16 toward the grinding wheel 14, which biases the workpiece 26 into engagement with the wheel 14 and the template 33 into engagement with the wear plate 61. At the beginning of the grinding operation the workpiece 26 is larger than the template 33. Therefore, the template does not contact the wear plate 61 until the workpiece has been ground down to the desired size, whereupon the template 33 contacts the wear plate 61, thus dictating the contour that will be ground into the workpiece and preventing further grinding thereof. The spring 28 is selected to be just strong enough to hold the stone 26 in contact with the wheel 14, but is not strong enough to overheat and fracture the stone.

So that the entire surface contour of the template 33 will be duplicated in the workpiece 26, the shanks 34 and 35 are periodically synchronously rotated in their respective spindles 37 and 39 by an indexing means 66.

The indexing means 66 comprises a solenoid 67 mounted by a suitable bracket 68 to the arm 15. The armature 69 of the solenoid 67 is connected by a link 70 to a vertically reciprocal slide bar 71. The opposite ends of the slide bar each have a shoe 72 pivotally mounted thereon for engaging the indexing wheels 40 and 41 to rotate them and thus rotate the template 33 and the workpiece 26.

The armature 69 of the solenoid 67 is biased to the extended position by a spring (not shown) within the solenoid, so that when the solenoid is energized the armature will retract and carry the slide bar 71 upwardly, and when the solenoid is deenergized, spring action will return the slide bar 71 to its downwardly disposed position.

The opposite ends of the slide bar 71 are each formed with an arcuate surface 73 and a flat surface 74 which coact with their respective shoes 72 to stop counterclockwise movement thereof (FIG. 1) when the shoes are pivoted to a substantially horizontal position, and allows pivot movement from the position in a clockwise direction.

This action may best be seen in FIGS. 6a-6c, wherein the lower shoe 72 is illustrated in a series of positions which rotate the index wheel 40 of the workpiece 27. The wheel 40 is provided with a plurality of notches 75 formed in spaced increments in the periphery thereof. A spring loaded detent pin 76 will register with the notches 75 and hold the workpiece stationary between subsequent rotations thereof. When the slide bar 71 is moved upwardly by the solenoid 67 being energized, the lower shoe 72 engages one of a plurality of extending pins 77a provided on the wheel 40. As seen in FIG. 6a, this will rotate the wheel so that the notch 75a is disengaged from the detent pin 76. FIG. 6b shows up ward movement of the slide bar 71 as having been completed which rotated .the indexing wheel 40 so that the notch 75b now engages the pin 76. FIG. 60 shows downward movement of the slide bar 71 as bringing the shoe 72 down into engagement with the upper surface of a pin 77b over which it slides due to pivot action of the shoe. When this downward movement of the slide bar 71 is completed the shoe 72 will be positioned below the pin 77b and will be ready for a subsequent energizing of the solenoid 67, which will cause repetition of this cycle.

As seen in FIG. 1, the upper indexing wheel 41 is provided with peripheral notches 78, detent pin 79 and extending pins 80 so that it operates in the same manner and in unison with the lower indexing wheel 40.

A cycle of rotation of the wheels 40 and 41 is initiated by a limit switch 80 which is coupled to the solenoid 67. The limit switch 80 is mounted on the support arm 16 at a location which is adjacent to lower edge 81 of the spindle 39. Therefore each time a cycle of reciprocating motion of spindles 37 and 39 is completed the limit switch 80 is contacted and causes the solenoid 67 to be energized.

Although but one embodiment of the present invention has been illustrated and described, it will be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the spirit of the invention or from the scope of the appended claims.

What is claimed is:

1. A gem grinding machine comprising in combination:

a base,

a rotatable grinding wheel mounted on said base,

a feed frame mounted on said base to move, relative to a grinding surface on said grinding wheel,

a support arm mounted on said feed frame for movement therewith,

biasing means mounted between said base and said support arm to normally urge said feed frame and said support arm toward said grinding wheel,

a first guide assembly mounted on said support arm,

a first spindle mounted on said first guide assembly for movement in an arcuate path defined by said first guide assembly,

a master template holding shank rotatably joumaled in said first spindle, said template holding shank having a master template on one end thereof,

a second guide assembly mounted on said support arm,

a second spindle mounted on said second guide assembly for movement in an arcuate path defined by said second guide assembly, the arcuate paths defined by said first and second guide assemblies being identical,

a workpiece holding shank rotatably joumaled on said second guide assembly, and adapted to support a grindable workpiece thereon at a grinding point of contact on the grinding surface of said grinding wheel,

drive means coupled to said first and second spindles for causing synchronous reciprocal movements thereof in their respective arcuate paths to produce a rocking motion of said workpiece holding shank about the grinding point of contact and producing a similar rocking movement of said template holding shank,

a wear plate mounted on said base and aligned with the grinding point of contact on said grinding wheel and aligned with the master template to provide a stop and bearing surface for the master template to control movement of the feed frame toward the grinding wheel, and

indexing means on said support arm and coupled to said first and second spindles for causing simultaneous periodic rotational movements thereof.

2. The gem grinding machine set forth in claim 1 in further combination with:

a limit switch mounted on said support arm and positioned thereon for engagement by one of said first and second spindles for actuating said limit switch each time one reciprocal movement of said one of said first and second spindles is completed,

said limit switch being coupled to said indexing means for controlling the periodic movement thereof.

3. The gem grinding machine set forth in claim 1 wherein said indexing means comprises:

a solenoid mounted on said support arm,

an indexing wheel mounted on said support arm, and

a slide bar movable by said solenoid for rotating said indexing wheel.

4. The gem grinding machine set forth in claim 1 wherein:

said template is removably mounted on said template holding shank for replacement purposes.

5. The gem grinding machine set forth in claim 1 wherein:

said support arm is pivotally adjustably mounted on said feed frame to compensate for wear of the grinding wheel. 

1. A gem grinding machine comprising in combination: a base, a rotatable grinding wheel mounted on said base, a feed frame mounted on said base to move, relative to a grinding surface on said grinding wheel, a support arm mounted on said feed frame for movement therewith, biasing means mounted between said base and said support arm to normally urge said feed frame and said support arm toward said grinding wheel, a first guide assembly mounted on said support arm, a first spindle mounted on said first guide assembly for movement in an arcuate path defined by said first guide assembly, a master template holding shank rotatably journaled in said first spindle, said template holding shank having a master template on one end thereof, a second guide assembly mounted on said support arm, a second spindle mounted on said second guide assembly for movement in an arcuate path defined by said second guide assembly, the arcuate paths defined by said first and second guide assemblies being identical, a workpiece holding shank rotatably journaled on said second guide assembly, and adapted to support a grindable workpiece thereon at a grinding point of contact on the grinding surface of said grinding wheel, drive means coupled to said first and second spindles for causing Synchronous reciprocal movements thereof in their respective arcuate paths to produce a rocking motion of said workpiece holding shank about the grinding point of contact and producing a similar rocking movement of said template holding shank, a wear plate mounted on said base and aligned with the grinding point of contact on said grinding wheel and aligned with the master template to provide a stop and bearing surface for the master template to control movement of the feed frame toward the grinding wheel, and indexing means on said support arm and coupled to said first and second spindles for causing simultaneous periodic rotational movements thereof.
 2. The gem grinding machine set forth in claim 1 in further combination with: a limit switch mounted on said support arm and positioned thereon for engagement by one of said first and second spindles for actuating said limit switch each time one reciprocal movement of said one of said first and second spindles is completed, said limit switch being coupled to said indexing means for controlling the periodic movement thereof.
 3. The gem grinding machine set forth in claim 1 wherein said indexing means comprises: a solenoid mounted on said support arm, an indexing wheel mounted on said support arm, and a slide bar movable by said solenoid for rotating said indexing wheel.
 4. The gem grinding machine set forth in claim 1 wherein: said template is removably mounted on said template holding shank for replacement purposes.
 5. The gem grinding machine set forth in claim 1 wherein: said support arm is pivotally adjustably mounted on said feed frame to compensate for wear of the grinding wheel. 